每日算法刷题 Day12- 跳台阶、排列、替换空格、求 n 累加

5

8

#include<bits/stdc++.h>using namespace std;
int n;int ans = 0;
void foo( int k){    if( k == n)ans++;    else if(k < n)    {        foo(k+1);        foo(k+2);    }}

int main(){    cin >>n;    foo(0);    cout << ans <<endl;    return 0;    }

#include<bits/stdc++.h>using namespace std;
int a[20];int n;

int main(){        cin >>n;    a[0] = 1;    for( int i = 1; i <= n; i++)    {        a[i] = a[i-1] + a[i-2];    }    cout <<a[n];    return 0;    }

3

1 2 31 3 22 1 32 3 13 1 23 2 1

#include<bits/stdc++.h>using namespace std;
int N = 10;int n;
void dfs(int u, int num[], bool st[]){    if(u > n)    {        for(int i = 1; i <= n; i++)cout << num[i]<< " ";        cout << endl;    }    else     {        for(int i = 1; i <= n; i++)            if (!st[i])            {                st[i] = true;                num[u] = i;                dfs( u +1 , num ,st);                st[i] = false;//恢复现场            }    }}

int main(){    int num[N];    bool st[N] = {0};//定义状态变量    cin >> n;    dfs(1,num,st);//从1开始排列    return 0;    }

输入："We are happy."
输出："We%20are%20happy."

class Solution {public:    string replaceSpaces(string &str) {        string res;        for(auto c : str)        {            if(c == ' ')res += "%20";            else res += c;        }        return res;    }};

输入：10
输出：55

class Solution {public:    int getSum(int n) {        int sum = n;        n > 0 && (sum += getSum(n - 1));        return sum;    }};